A rational expression is defined as a fraction where both the numerator and the denominator are polynomials. Let's evaluate the options:
A) \( \frac{5.3}{2x - 1} \) - The numerator (5.3) is a constant (which is a polynomial of degree 0) and the denominator (2x - 1) is a polynomial of degree 1. This is a rational expression.
B) \( \frac{x^3}{2} + \frac{5}{2x^9} \) - The first part \( \frac{x^3}{2} \) is a polynomial term, but the second part \( \frac{5}{2x^9} \) does not form a single rational expression because of division by a variable raised to a power in the denominator.
C) \( \frac{8x^2 + 7}{0} \) - Division by zero is undefined, so this does not qualify as a rational expression.
D) \( \frac{9x - 4}{8 + \sqrt{x}} \) - The denominator \( 8 + \sqrt{x} \) is not a polynomial because \( \sqrt{x} \) is not a polynomial term.
The only correct answer among the options provided is:
A) \( \frac{5.3}{2x - 1} \).